This disclosure relates to conveyor elements for the transport of bulk materials such as coal and the like, and, more particularly, to chain used in connection with longwall conveyor systems.
More particularly, this disclosure relates to a link chain formed of a sequence of individual, consecutive chain links linked with one another. The link chain has an arrangement that prevents or minimizes misalignment of the link chain.
A longwall conveyor system includes a pan and a coal conveying chain and flight mechanism thereon. The coal conveying mechanism includes a sprocket drive that pulls the chain and flight mechanism along the pan. The flights are attached to the chain at spaced intervals. As the chain and flights move along the pan, coal is carried by the flights to the end of the pan, where it is transferred to a mechanism for taking the coal out of the underground mine.
Link chains consist of a plurality of individual chain links linked with one another. In the case of link chains for industrial applications, such as, for example, a conveyor chain for use in underground coal mining, the individual chain links are subjected to extremely high tensile stress.
A link chain demonstrates its maximum ability to withstand tensile stress when the individual chain links are disposed one after the other in an intended manner such that the inside portions of two facing arcs of two consecutive chain links rest against one another. The rated ability of a link chain to withstand stress regularly presupposes that the chain links of the link chain that is subject to the tensile stress are disposed, relative to one another, in the intended manner described above.
Mining chain comprises welded wire links or welded wire links lased to forged links, where the individual links are oval in shape. Some chains incorporate a link with a cross member or dividing element that forms a “figure of 8” link to limit the amount of moment that can occur between the individual links, thereby preventing the chain from knuckling. This geometry is extensively used on anchor chains, where knuckling would prevent the chain being safely stowed onboard ship. However, the figure of 8 link is very stiff as the cross member prevents the crown and sides of the link breathing and flexing together. Highly loaded mining chain requires a level of flexibility to enable it to with stand shock loading typical seen on scrapper conveyors.
An example of such a chain can be found in GB 693734A, from which prior art FIGS. 1 to 3 are reproduced herein. In this chain, the chain shown is formed by links 1 of a normal round-wire type and links 2 of a novel type having plane edges. The links 1 and 2 succeed one another in the chain alternately and they engage one another therein in the manner illustrated. The links 1 are, for example, calibrated links of marine chains, their internal length or pitch being P2, their width B, and the diameter of the wire of which they are composed d. The links 2 each consist of a plate of flattened oval form, that is, each consists of an oval plate the rounded ends of which are connected by plane or nearly plane surfaces. The said plate, which is fashioned by cutting or forging, for example, has a width A that is smaller than the width B of links 1, and is formed with two holes 3 and 4 limited by toroidal surfaces, with a dividing element 8 there between. The said holes are so dimensioned and positioned as to receive, respectively, the neighboring ends 11 and 111 of the adjacent links 1 and to permit the articulation of these links in all directions with respect to the link 2. To this end, the holes 3 and 4 are made with a diameter slightly larger than d, and the toroidal surfaces limiting these holes are adapted to make them fit, at least approximately, along the inner surface of the ends 11 and 111. The spacing between the holes 3 and 4 is preferably so chosen that the distance P1 separating the extreme edges of the holes is equal to the internal length P2 of the links 1. The thickness e of the links 2 is smaller than the internal width b of the links 1 and is sufficient to enable the link 2 to resist the pull exerted thereon in use. For example e may be equal to d.